One of the principal error sources for a gyroscope is bias instability due to temperature fluctuations. In particular, most of the long term drift in the bias stability of present gyroscopes is believed to be due to slow temperature drifts in the gyroscope packaging.
For expensive gyroscopes, temperature compensation and/or ovenization are utilized to correct and/or control the temperature of the gyroscope. However, the prior art temperature compensated and/or oversized gyroscopes have required large modules having several cubic inches of volume. These prior art modules also consumed several watts of power. These factors increase the cost and limit the applications for which these expensive gyroscopes can be used.
For low cost MEMS (micro-electro-mechanical system) gyroscopes, temperature control has not been commercially utilized. However, the result is less than sufficient bias stability and therefore less accuracy for navigational grade gyroscopes. Research at the University of Michigan has demonstrated on-chip ovenization of gyroscopes under a DARPA program named HERMIT. This prior art uses simple Si (silicon) based thermistors to detect temperature fluctuations near the gyroscope in order to correct and/or control the temperature of the gyroscope. However, Si thermistors have accuracies in the 10-100 mK range, and because a Si disk resonator gyroscope (DRG) has a predicted bias drift sensitivity of 10°/hr/° C., controlling the temperature to within 10 mK yields a bias stability of 0.1°/hr, which is not a sufficient stability for many applications.
The need for low cost gyroscopes is increasing due to many expanding applications including micro UAVs, satellites, and handheld GPS (global positioning satellite) systems. A particular need for low cost gyroscopes with both military and commercial applications is for personal tracking systems, which are becoming more common.
What is needed is a low cost gyroscope with low volume and power requirements. Also needed is a low cost gyroscope with improved bias stability. The embodiments of the present disclosure answer these and other needs.